This study examines traffic-related air pollution in London in relation to area- and individual-level socio-economic position (SEP). Mean air pollution concentrations were generally higher in postcodes of low SEP as classified by small-area markers of deprivation (Index of Multiple Deprivation (IMD) domains) and by the postcode-level ACORN geodemographic marker. There were exceptions, however, including reversed directions of associations in central London and for SEP markers relating to education. ACORN predicted air pollution independently of IMD and explained additional variation at the postcode level, indicating the potential value of using both markers in air pollution epidemiology studies. By contrast, after including IMD and ACORN there remained little relationship between air pollution and individual-level SEP or smoking, suggesting limited residual socio-economic confounding in epidemiological studies with comprehensive area-level adjustment.